Y Miyoshi, Y Bugoslavsky, S K Clowes, W R Branford, C. Grigorescu, S A Manea, O Monnereau, L F Cohen, Spin polarisation of the transport current at the free surface of bulk NiMnSb, Physical Review B 69 (2004) 214425-1 ­– 214425-5

Title: Spin polarisation of the transport current at the free surface of bulk NiMnSb

Abstract: The point contact Andreev reflection employing niobium tips was used to determine the degree of transport current spin polarization (P-t) at the free surface of bulk NiMnSb at 4.2 K. The data was analyzed within the framework of a modified version of the Blonder, Tinkham, and Klapwijk formulism taking into account the two spin polarized channels in the ferromagnet and treating the interface as a planar delta function barrier of height Z between free electron materials. We find that the measured spin polarization is rather insensitive to different surface preparations and magnetic domain structure, and the maximal value of the P-t at Z=0 is 44%, consistent with recent calculations of the surface reconstruction of NiMnSb. Saturation magnetization of the samples was found to be 3.6 mu(B) per formula unit indicative of a small amount of atomic disorder.

Key words: Half-Metallic Ferromagnet; Electronic-Structure; Andreev Reflection; Heusler Alloys; Point-Contact; Thin-Films; Injection; Spintronics